The present invention relates generally to keyboard apparatus provided in electronic keyboard instruments etc., and more particularly to a keyboard apparatus provided with force sense control and operation control functions for controlling an operational feeling and behavior of keys.
Keyboard units of natural keyboard instruments, such as acoustic pianos, which generate raw tones, are constructed to generate a tone by a hammer, pivoting in response to depression of a key, striking strings. In these keyboard units, an action mechanism, including a jack and a wippen, is provided between each key and a corresponding hammer. Such an action mechanism allows a characteristic reaction force to be applied from the key to a human player's finger. Thus, in the keyboard unit of a natural keyboard instrument, a key touch feeling characteristic of, or unique to, the keyboard instrument can be obtained.
Keyboard units of electronic keyboard instruments which generate electronic tones, on the other hand, include, among others, a spring and a mass member (pseudo hammer) for returning a depressed key to an initial position, and these keyboard units simulate a key touch feeling of a natural keyboard instrument through a reaction force provided by the spring and mass member. However, in the electronic keyboard instruments, which generate an electronic tone in response to depression of a key, there is provided no mechanism that actually strikes strings to generate an electronic tone and hence no complicated action mechanism as in the natural keyboard instruments. Consequently, the keyboard units of the electronic keyboard instruments cannot faithfully reproduce a key touch feeling provided through the action mechanism of the natural keyboard instruments, and thus, strictly speaking, the key touch feeling provided by the electronic keyboard instruments is different from that provided by the natural keyboard instruments.
Therefore, in the field of the electronic keyboard instruments, there have been proposed key drive and control devices (force sense control means) for changing a reaction force responsive to depression of a key with a view to achieving behavior of the key and key touch feeling approximate to that provided by the natural keyboard instruments. For example, a keyboard unit disclosed in Japanese Patent No. 2956180 (hereinafter referred to as “Patent Literature 1”) includes an actuator (solenoid) for driving a key and a control means for controlling the actuator. Thus, the keyboard unit disclosed in Patent Literature 1 can simulate a performance feeling of a natural keyboard instrument by appropriately adjusting a key touch feeling.
Further, in a keyboard apparatus disclosed in Japanese Patent No. 3644136 (hereinafter referred to as “Patent Literature 2”), a key is normally biased in both of key-depressing and key-releasing directions by springs, acting in the key-depressing and key-releasing directions, respectively, so that the key is balanced at its rest position. The key is driven by a bidirectional actuator, so that the disclosed keyboard apparatus can achieve both force sense control on key depression and an automatic performance.
Furthermore, a keyboard apparatus disclosed in Japanese Patent Application Laid-open Publication No. 2005-195619 (hereinafter referred to as “Patent Literature 3”) includes a mass member simulating a hammer member of an acoustic piano, and an inertial load of the mass member is imparted as a reaction force to operation of a corresponding key. The disclosed keyboard apparatus has a force sense control function in which other necessary viscous, elastic and frictional loads etc. are generated by an actuator (solenoid). The keyboard apparatus disclosed in Patent Literature 3 can create a key touch feeling approximate to that of an acoustic piano through cooperation between the mass member and the actuator.
With the keyboard unit disclosed in Patent Literature 1, where behavior of the key is controlled by the solenoid alone, it is difficult to replicate or reproduce a key touch feeling of an acoustic piano with high accuracy. Further, the keyboard apparatus disclosed in Patent Literature 2 includes the key-biasing springs as main elements for controlling behavior of the key. However, in the case where the behavior of the key is controlled by the springs, even if auxiliary force sense control of the key is performed through driving of the actuator, the keyboard apparatus disclosed in Patent Literature 2 cannot faithfully reproduce an inertial mass feeling characteristic of behavior of a key of a natural keyboard instrument, such as an acoustic piano. Particularly, whereas, in an acoustic piano, movement of a key has to be started at the start of depression of the key against a static load of a string-striking hammer, it is difficult for the keyboard apparatus disclosed in Patent Literature 2 to appropriately reproduce an operational feeling at the start of depression of a key on an acoustic piano. Further, even if the springs provided in the keyboard apparatus disclosed in Patent Literature 2 are replaced with a mass member that generates an inertial force in interlocked relation to movement of the key, a possibility of properly controlling a load applied from the mass member to the key through driving of the actuator would be limited because the mass member is provided separately from the actuator and because the mass member and the actuator differ in operating system. Therefore, it is necessary to further improve the keyboard apparatus, in order to create a key touch feeling more approximate to that of a natural keyboard instrument and permit an automatic performance with smooth movement of the keys.
Further, in the keyboard apparatus disclosed in Patent Literature 3, the actuator is provided in abutment with the key so as to directly impart a reaction force to the key. Further, although the mass member is also provided in abutment with the key so as to interlock with the movement of the key, it is not in abutment with the actuator; namely, the mass member and the actuator are provided separately from each other. Thus, the mass member and the actuator have different operating systems, so that there are limitations to appropriately controlling, through driving of the actuator, a load applied from the mass member to the key.
Further, in the known keyboard apparatuses including a key and a mass member operating in interlocked relation to the key, a driving force is transmitted between the key or mass member and another component part interposed therebetween in a driving force transmission path between the key and the mass member. Often, the key or mass member and the other component part perform mutually-different movement, such as pivoting movement and linear movement, in the force transmission path. In this case, in order to achieve a more natural operational feeling through force sense control, it is necessary to make an arrangement such that an appropriate frictional force is produced against relative movement between the key or mass member and the other component part while still securing interlocked movement between the key or mass member and the other component part. Because, a key touch feeling achieved by an action mechanism provided in an acoustic piano is created by differently-operating component parts, such as a spin roller, jack rod and hammer, moving relative to one another while involving appropriate friction thereamong, and it is required to reproduce the key touch feeling as faithfully as possible in the keyboard apparatus.
Furthermore, the keyboard apparatus disclosed in Patent Literatures 1 and 2 are constructed to simulate a key touch feeling of an acoustic piano by controlling the driving of the actuator that imparts a reaction force to the key. However, in natural keyboard instruments, such as an acoustic piano, including a complicated action mechanism, there is produced, during each of key depression and key release operation, a characteristic key touch feeling with an intensity of a reaction force varying from moment to moment in response to a changing key position (i.e., key depression amount), key velocity, etc. In order to faithfully reproduce such a key touch feeling of a natural keyboard instrument, there is a need to make further improvements in the driving control of the actuator performed in the conventionally-known keyboard apparatus.